I am planning on changing the vinyl siding on my house and I'm going to add 2" of extruded polystyrene. I only have R12 in my 2x4 walls and figure I'd be an idiot not to add exterior insulation before re-siding the house. I keep hearing conflicting installation techniques. I am going to use polystyrene that is shiplapped and I want to use "tucktape" on the seams. I will be using a "Typar" house wrap on top of the polystyrene. Some people including the company that is installing the siding, tell me NOT to seal the seams because moisture has to be able to escape. the Dow Corning web site says to seal the seams.

What is the proper technique.